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Reliable information on embryonic and fetal development of the human oro-facial system is meager. Much of the data available at present is not entirely reliable, because it was derived from a small number of specimens. An embryological approach with human materials is important for establishing a normal standard of development including individual variabilities as well as clarifying the embryogenesis and etiology of defective development (Nishimura et al. 1977). It is important in human craniofacial embryology to know the variabilities, that is, individual differences in developmental phenomena of the oro-facial region during human prenatal life. In recent times the importance of morphologic investigations of human development has received less emphasis. Yet, without thorough knowledge of the basic facts of prenatal human development, erroneous assumptions can be made in more dynamic approaches and lead investigators astray. Knowledge of prenatal development of human orofacial structures and some of their deviations will therefore be welcomed by many basic scientists and clinicians in the field of facial clefts and other craniofacial malformations. The author was engaged in the collection and systematic study of human embryos and fetuses with Dr. Hideo Nishimura, Emeritus Professor of Kyoto University, Kyoto, Japan, and has been studying the normal and abnormal development during prenatal life. Several results obtained from the study of a large number of specimens are presented laying stress on the orofacial development.

In the sagittal plane the interplay of the knee joints, the patellofemoral and the tibiofemoral joint, are depicted as a closed kinematic chain consisting of 3 dimeric link chains. Kinematically the system is without constraint and possesses 3 (abstract) degrees of freedom. Only the application of external forces fixes the single dimeric link chains in mechanically stable positions and thus determines the momentary functional state of the knee. Without external loads the single links can snarl up like those of a bike's chain. The crucial ligaments play a minor role for knee bending. A qualitative analysis of the force distribution within the knee is presented. In the frontal plane the tibiofemoral joint represents a linkquadrangle with positive drive (one abstract degree of freedom) which also becomes mechanically stable by external compressive forces.

The biomechanical process which lead to the development of cracking sounds in the temporomandibular joints have received contradictory treatment in the literature. Most of the authors regard consider the cracking sounds to be caused by mechanical friction produced in translational movements of the condylus. According to this hypothesis the discus articularis which is dislocated in an anterior direction active pulling of the lateral pterygoid muscle, is regarded as being a mechanical obstacle. The morphological relationships however, between the lateral pterygoid muscle and the discus articularis are unclear. Our histomorphological investigations of 16 human temporomandibular joint samples from fresh cadavers of victims of accidental death revealed evidence that in the majority of cases a tendon connected the upper head of the lateral pterygoid muscle with the discus articularis. This would suggest that an anterior dislocation of the discus, resulting from an active pulling movement of the lateral pterygoid muscle, cannot be ruled out as a possible morphological cause for cracking sounds.

Canine anterior cruciate ligaments were sectioned into sagittal, frontal and horizontal segments which were stained in bulk using a modified gold chloride method. Segments were then serially sectioned on a sliding microtome at 100 micron, mounted on slides, dehydrated and coverslipped. Abundant Ruffini and pacinian receptors were identified within the substance of the ligament. These receptors were innervated by 5 to 10 micron diameter axons penetrating from the peripheral synovium investing the ligament. The anterior cruciate ligament is capable of afferent input to the central nervous system of importance to the biomechanical function of the knee joint.

The structure of the house musk shrew (Suncus murinus) ovary, prepared by the Osmium-DMSO-Osmium method, was examined with a scanning electron microscope. Many ovarian follicles in various stages of development can be seen in the musk shrew ovary, but fully matured follicles (Graafian follicles) are never observed. In the inner layer of zona granulosa of the preantral follicles, the follicular cells containing a large amount of glycogen deposition in the cytoplasm are observed. Folded and collapsed zona pellucida surrounding the remnant of the degenerated oocyte, which is thought to be a residual form of atretic follicle, is observed in a small, crypt-like depression on the surface of the ovary where it has been split by cracking.

Quantifications in parasympathetic ganglia are not available in literature. The otic ganglia of 9 Wistar rats were studied (thick and semi-thin sections) in order to determine the following quantitative data: ganglionic volume (GV), neuronal volume density (Vv), neuronal cellular surface per cell volume (Sv), and neuronal numerical density (Nv). The results showed (mean +/- SD): GV = 0.31 +/- 0.05 mm3, Vv = 39.62 +/- 12.25%, Sv = 0.169 +/- 0.056 microns-1 and Nv = 3.84 x 10(-5) +/- 1.69 x 10(-5) microns-3. These determinations provide a basis for comparisons of parasympathetic with sympathetic ganglia.

When hydrocortisone acetate was administered subcutaneously to the lactent Brazilian white belly opossum, it induced precocious intestinal maturation. Histological features of the small intestine were reminiscent of those seen in human protein-caloric malnutrition. There were also indications that the glucocorticoid acted as an inducer of the differentiation of Paneth, goblet and granulomucous cells within the small intestinal epithelium. In the lactent opossum the small intestine is lined by an epithelium containing cells which exhibit intense endocytic activity (Krause et al. 1977; Santiago et al. 1983; H.B. Coutinho, Beck--unpublished) verified that subcutaneous injections of hydrocortisone acetate could determine intestinal closure in lactent opossums. Krause et al. and Santiago et al. have reported that in Didelphis virginiana and Didelphis albiventris, respectively, the goblet cells and Paneth cells differentiate lately in the development of pouch opossum young. Freitas et al. (1982) mentioned that the plasma cortisol level was very low in lactent white belly opossum, but preceding weaning there was an abrupt increase of the plasma cortisol reaching levels comparable to that obtained in adult animals. These facts suggested the need for investigations to clarify if cortisol could act as an inductive agent for the differentiation of goblet cells and Paneth cells in the lactent D. albiventris.

The arising patterns of the bovine diaphragmatic crura which consists of right and left crura in the lumbar portion of diaphragm, and the relative muscle weight of each crus were investigated. Diaphragm was obtained from 61 just before birth stage bovine fetus. The arising formation of the diaphragmatic crura in this study achieved its adults form. The arising patterns of the diaphragmatic crura were classified into 3 types according to the pattern of the cranial end of attachment of tendons in the right and left crura. The cranial end of the attachment of tendon is cranial in the right crus than in the left, shows the highest relative muscle weight of the right crus. The cranial end of the attachment of tendon is cranial in the left crus than in the right, shows the highest relative muscle weight of the left crus.

The straight sinus was examined in 56 human cadavers. In 26.7% of the cadavers the straight sinus was double, being either median in position, that is, one was superior and the other inferior (17.8%) or paramedian, that is, both lay side on either side of the midline at the junction of the falx cerebri with tentorium cerebelli (8.9%). In 2 cases (3.5%) of the cadavers the straight sinus was triple, being either median in position or paramedian.

As part of a comparative morphological study, the fine structure of the retinal pigment epithelium (RPE), the choriocapillaris and Bruch's membrane (complexus basalis) has been studied by electron microscopy in the brush-tailed possum (Trichosurus vulpecula), an Australian marsupial. In this species, the RPE consists of a single layer of squamous cells which show numerous shallow basal (scleral) infoldings as well as extensive apical (vitreal) processes enclosing rod outer segments. The epithelial cells are joined laterally by prominent, apically-located tight junctions. Internally smooth endoplasmic reticulum is the most abundant cell organelle with only small amounts of rough endoplasmic reticulum present. Basally-located mitochondria and apically-located melanosomes are abundant while polysomes and the occasional Golgi zone are also noted. The epithelial cell nucleus is large and vesicular. Bruch's membrane shows the typical pentalaminate structure noted for mammalian species. The choriocapillaris is a single layer of anastomosing capillaries which are heavily fenestrated facing the retinal epithelium.